Circuit for controlling light displays and the like

ABSTRACT

A circuit for controlling activation of lamps in a light display by an A.C. source includes a clock for generating a sequence of clock pulses, and a shift register for storing a plurality of electrical representations and for successively altering the stored representations in response to receive clock pulses. Also included is switch apparatus responsive to the signal representations stored in the shift register for producing a set of signals which enable activation of selected ones of the lamps by the alternating current source. A clamping circuit prevents application of clock pulses to the shift register during alternate half cycles of the A.C. source, and an array of switches enable activation of the selected lamps only during the alternate half cycles. In this manner, lamps are activated only at or near zero crossover of the A.C. source output.

United States Patent 1191 White 1 Sept. 30, 1975 CIRCUIT FOR CONTROLLINGLIGHT DISPLAYS AND THE LIKE Laurence Clark White, 1357 28th St., Ogden,Utah 84403 [22] Filed: Sept. 25, 1974 [21] Appl. No.: 508,988

[76] Inventor:

[52] US. Cl l. 315/250; 315/316 511 int. c1. ..n05B 37/00; HOSB 39/00;

[58] Field of Search 315/250, 315, 316

[56] References Cited UNITED STATES PATENTS 3.706.914 12/1972 Van Burcn315/316 $763,394 10/1973 Blanchard 315/315 X Primary E.\-aminerPalmcr C.Demco Attorney. Agent, or FirmCriddle & Thorpe l I I I I I I II I: I III D.C. Power StppIy l0 Clamping Circuit 18' 26a 26b 26c I l 5 7 ABSTRACTA circuit for controlling activation of lamps in a light display by anA.C. source includes a clock for generating a sequence of clock pulses,and a shift register for storing a plurality of electricalrepresentations and for successively altering the stored representationsin response to receive clock pulses. Also included is switch apparatusresponsive to the signal representations stored in the shift registerfor producing a set of signals which enable activation of selected onesof the lamps by the alternating current source. A clamping circuitprevents application of clock pulses to the shift register duringalternate half cycles of the A.C. source, and an array of switchesenable activation of the selected lamps only during the alternate halfcycles. In this manner. lamps are activated only at or near zerocrossover of the A.C. source output.

15 Claims, 1 Drawing Figure :Shift Register 22 l l I Function Switch 30CIRCUIT FOR CONTROLLING LIGHT DISPLAYS AND THE LIKE BACKGROUND OF THEINVENTION This invention relates to apparatus for controlling theactivation of light displays and the like.

Light and other visual displays are used extensively in advertising andmarketing. Such displays oftentimes include either moving or changingpatterns of lights and, of course, control apparatus must be employed toproperly sequence the light patterns displayed, i.e., to control theturnon and turnoff of the lamps used to create the display.

Light display control apparatus in general use at the present timeutilizes mechanical switches to turn on and turn off the lamps of thedisplay. The switches respond to sequencing apparatus to effect turnonand turnoff of the lamps at random points in the waveform of the A.C.source signal. That is, a lamp might be turned on or turned off at thepeak of the positive half cycle of the A.C. source waveform or at anyother point therein. Because of this, electromagnetic waves aregenerated when the lamps are turned off or turned on and these wavestend to interfere with local radio and television signals. Further,since lamp turnon may occur at a peak of a half cycle of the A.C.source, a large instantaneous current inrush to the lamps might resultand this tends to reduce the life of a lamp.

With the typically used mechanical control apparatus, it is difficult tovary the time during which lamps or lamp patterns are either on or off.Generally, some mechanical change must be made in order to do this andsuch changes are time consuming and costly. Finally, because suchcontrol apparatus consists of me chanical parts, the apparatus is bulky,heavy and subject to fairly rapid wear.

Some of these problems can be overcome by electronic apparatus such asthat described in an article entitled A Designers Compendium of FlashingLight Circuits, EDN, July 5, 1974, pp. 84-93. Included in the articleare descriptions of circuits which use shift registers for producingdifferent signal patterns depending upon the contents of the registers.These circuits are more compact and reliable, but the problem ofunwanted generation of electromagnetic waves still exists.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a compact, reliable and long lasting circuit for controllinglight displays and the like.

It is also an object of the present invention to provide such a controlcircuit in which very little electromagnetic radiation is generated.

It is still another object of the present invention to provide such acontrol circuit in which the turnon and turnoff of the electricalelements to be controlled occurs at or near zero crossover of the signalwaveform output of the A.C. source used to energize the display.

It is an additional object of the present invention in accordance withone aspect thereof to provide such a control circuit in which the periodof turnon and turnoff of the display elements may be readily varied.

It is a further object of the present invention in accordance withanother aspect thereof to provide such a control circuit in whichapplication of power to the electrical elements of the display isallowed only during alternate half cycles of the A.C. source.

The above and other objects of the present invention are realized in aspecific illustrative embodiment of a control circuit capable ofcontrolling the activation of a plurality of electrical elements by anA.C. supply in which the circuit includes circuitry responsive tosuecessively received signal patterns for selectively enabling theactivation of the electrical elements by the A.C. supply, and circuitryfor producing the signal patterns and for changing from one signalpattern to a succeeding signal pattern at or near zero crossover of thewaveform of the output of the A.C. supply. The electrical elementsactivated at any particular time are determined by the signal patternthen persisting. By enabling activation of the electrical elements atzero crossover, very little electromagnetic radiation is generated andtherefore very little interference with local radio and televisiontransmission occurs. The circuitry provided is all electronic andtherefore long lasting and reliable.

BRIEF DESCRIPTION OF THE DRAWING The objects, features and advantages ofthe present invention will become apparent from a consideration of thefollowing detailed description presented in connection with theaccompanying drawing which shows one illustrative embodiment of acircuit for controlling lamp displays and the like made in accordancewith the principles of the present invention.

DETAILED DESCRIPTION The circuit shown in the drawing is connectedbetween an A.C. supply 2 and a. plurality of lamps 6a through 6d.Although the circuit of the drawing will be described in connection withcontrolling the turnon and turnoff of lamps 6a through 6d, it should beunderstood that the circuit could be utilized for controlling activationofa variety of other electrical elements such as solenoids, electricalswitches, etc.

The circuit of the drawing includes a DC. power supply 10 coupleddirectly to the A.C. supply 2, a clock circuit 14 which is powered bythe DC. power supply 10, a clamping circuit 18 coupled to the A.C.supply 2 and to the output of the clock circuit 14, and a multistageshift register 22 coupled to the output of the clamping circuit 18. Eachstage of the shift register 22, consisting of a plurality of bistablestorage elements 26a through 26e, is coupled to a function switch ortranslator 30. The function switch 30 includes a plurality of outputs,some of which are coupled to gate electrodes of a plurality ofsilicon-controlled rectifiers (SCRs) 34a through 34d, others of whichare connected to a NOR gate 38, and still others of which are connectedto bistable element 26a. The output of the NOR gate 38 is coupled by wayof a pair of inverters 42 to the input of the bistable element 26a. Thepower electrodes (cathode and anode) of the SCRs 34a through 34d areeach coupled in series between ground potential and a different one ofthe lamps 6a through 6d which are, in turn, coupled to the A.C. supply2. It should be understood that although only five bistable elements areshown for the shift register 22 and only four SCRs and four lamps areshown, either a greater or lesser number could be provided as desired bythe user.

Before describing the details of the circuit of the drawing and of theoperation thereof, a general description of the operation will be given.The DC power supply activates the clock circuit 14 to produce and supplyto the clamping circuit 18 a sequence of positive-going clock pulses.The clamping circuit 18 is responsive to the output of the A.C. supply 2to pre'- vent application of the clock pulses to the shift register 22during every other half cycle of the A.C. supply output and particularlyduring every positive half cycle of the A.C. supply output. Each time aclock pulse is sup plied to the shift register 22, signalrepresentations stored therein are altered or changed in accordance withthe interconnections between the shift register and the function switch30. The outputs of the shift register 22 are supplied to the functionswitch which may or may not translate or alter this output, dependingupon the internal wiring of the function switch, and the function switchthen supplies a set of signals to selected ones of the SCRs 34a through340' to place the selected SCRs in a conducting condition; Those lamps6a through 6d which are connected to the conducting SCRs are therebyactivated by the A.C. supply 2 during positive half cycles of the outputof the A.C. supply. In this manner, the sequence of turnon and turnoffof the lamps 6a through 6d is controlled to thereby provide differentlamp activation patterns. The change from one lamp pattern to anotheroccurs at or near zero crossover of the A.C. supply output and thereforelittle electromagnetic radiation is generated so that very little radioand television signal interference will occur. Also, instantaneousinrush of current to. the lamps is eliminated so lamp life is extended.A more detailed description of the circuit of the drawing will now i begiven.

The DC. power supply 10 is included in the circuit to provide the clockcircuit 14 and other components of the circuit with DC. power. Thesupply 10 includes a resistor R1 connected to the A.C. supply 2 and adiode D1 for rectifying current from the supply. The anode of the diodeD1 is connected to the resistor R1 and the cathode is connected to thecathode of a zener diode D2. The anode of the zener diode D2 is coupledto ground potential. A capacitor C1 is coupled in parallel with thezener diode D2 and is provided for storing I a positive charge suppliedvia the resistor R1 and diode D1 from the A.C. supply 2. The zener diodeD2 pre' vents the voltage level across the capacitor C1 from exceedingsome predetermined value equal to the breakover voltage of the zenerdiode..The configuration of the DC. power supply 10operates to convertthe output of the A.C. supply 2 to a DC. voltage which is supplied tothe clock circuit 14.

The clock circuit 14 is a standard circuit which, throughthreshold-triggered charge-discharge cycles. of a capacitor C2, producesa sequence of clock pulses which are supplied to an inverter 1. Forexample, the timer designated NE 555 produced by Signetics Corp. mightillustratively be utilized as the clock circuit 14.

The clock circuit 14 includes a pair of variable resistors R2 andR3,'the first of which controls the charge time of a capacitor C2 andthus theinterval between clock The negative-going pulse output of theclock circuit anode of the diode D3 is connected to ground potential.The emitter and base electrodes of the transistor Q are coupled betweena resistor R5 and ground potential and the resistor. R5 couples theinverter 1 to the shift register 22. The capacitor C4 serves to phaseshift the outputof the A.C. supply 2 and the diode D3 serves to protectthe base-emitter junction of the transistor Q r from the negative halfcycles of the A.C. supply output.

The clamping circuit 18 operates to .clamp the output of the clockcircuit 14 to ground on positive half cycles'of the A.C. supply output.In particular, on positive half cycles'of the A.C. supply 2 which aresupplied via the capacitor C4 and resistor R4 to the base of thetransistor Q, the transistor is placed in a conducting condition so thatany signal applied by the clock circuit 14 via the inverter I to theresistor R5 is conducted to ground by the transistor Q. During negativehalf cycles of the output of the A.C. supply 2, the transistor Q isbiased into a nonconducting condition so that the output of the clockcircuit 14 is supplied to the shift register 22.

Clock pulses which are allowed to reach the shift register 22 areapplied to the clock C of each of the bistable elements 26a through 26c.The shift register 22 is provided for storing signal representationswhich, as

already mentiond,are used to define activation patterns of the lamps 6athrough 6d. Each of the bistable.

elements 26a through 262 is a type D master-slave flipflops andoperates, in response to a clock pulse on its clock input terminal, toapply to its Q output whatever i signal level is present on its D inputterminal. For exampulses. and the second of which controls the dischargeI time a clock pulse were received on the ClOCkillPUt C of the element,thenthe high level would be applied to the Q outputof the element. The 6output of each element'is the complement of the Q output of the element.That is, when the Q-output is high, the (j output is low and vice-versa.A positive-going pulse or high level on the reset input R of a bistableelement causes that element to assume a condition in which a low levelor a logical 0" is being produced on the Q output and a high level orlogical 1 is being produced on the 0 output.

The Q outputs of the bistable elements 26a through 26e are connected viainverters to a function switch 30. The function switch 30 utilizes theseoutputs to (1) apply sets of signals via resistors R8 to the gateelectrodes. of SCRs 34a through 34d, and '(2) to apply other sets ofsignals to various ones of the'bistable elements 26a through 26c toeffect changes in the signal representations stored in the elements.Thelatter sets of signals are applied tothe shift register 22 by a resetlead 46 which is coupled through a pairof inverters 50 to the resetinputs. R of bistable elements 26a through inverters 62 and 66 to theclock input Cland reset input R respectively of the bistable element26e. The particular configuration of the drawing by which the functionswitch 30 applies signals to the shift register 22 is illustrative andit should be recognized that a variety of configurations may be providedfor applying signals to the shift register 22 to thereby alter itscontents. The

particular configuration selected would be in accordance with the needsof the user. Similarly, the specific internal construction of thefunction switch 30 would be selected according to the needs of the userand an illustrative construction only as shown by dotted line in thedrawing. The operation of the shift register 22 and function switch 30to activate the lamps 6a through 6d will now be described for theillustrative circuit of the drawing.

Assume that each of the elements 26a through 26e are in the resetcondition so that each Q output is low and each 6 output is high. Sincetheinputs to the NOR gate 38 are grounded or low (as indicated by thedotted line interconnection of the function switch 30), the output ofthe NOR gate is high and high level is applied to the D input of element26a. Upon receipt of a clock pulse from the clock circuit 14 (whichpulse would be received during a negative half cycle of the output ofthe A.C. supply 2, as previously discussed), the high level on the Dinput of the first bistable element 26a is shifted to the Q output ofthe element. The Q outputs of elements 26a through 26e, after receipt ofthe clock pulse, and as represented by logical 0 and 1 notation, is10000, where the logical 1 represents a high level on output Q ofelement 26a and the logical Os" represent low leygls on the Q outputs ofelements 26b through 26e. The Q output of element 26a is thus low, butthis low level is inverted to a high level forapplication via thefunction switch 30 to the gate electrode of SCR 34a. SCR 34a is thusenabled to conduct current from the A.C. supply 2 through the lamp 6a toground on succeeding positive half cycles of the A.C. supply output.

On the next clock pulse received by the shift register 22, the highlevel on the 0 output of element 26a is shifted to the Q output ofelement 26b and the high level on the D input of element 26a is shiftedto the elements Q output. The Q outputs of elements 260 through 26eafter this clock pulse are thus 11000 and lamp 6b, as well as lamp 6a,is activated. On the next two clock pulses, the Q outputs of elements26a through 26e change successively to 1110 and then to 11110 toactivate lamp 6c and then lamp 6d. After all lamps have been activated,the next received clock pulse causes the Q output of element 262 tobecome low and this output is inverted to cause elements 260 through 26dto reset. The Q outputs of the elements are then 00001 and all lamps areextinguished. Upon receipt of the next clock pulse, the above sequenceof activating the lamp is repeated.

In the manner described, different ones of the lamps 6a through 6d aresuccessively activated, of course, as determined by the state of thebistable elements 26a through 26e of the shift register 22 and by theinternal wiring of the function switch 30. The sequence of activatingthe lamps may be changed simply by appropriate internal wiring of thefunction switch 30.

Since a clock pulse may be applied to the shift register 22 only duringnegative half cycles of the output of the A.C. supply 2, and since theSCRs 34a through 34d may conduct only during positive half cycles of theoutput, the change or switching from one pattern of activation of thelamps to another can only occur at the beginning of the positive halfcycles of the A.C. supply output, i.e., only at zero crossover of theoutput. Because of this, very little electromagnetic radiation isgenerated at the time of switchover or change of lamp patterns so thatvery little interference would occur with local radio and televisiontransmission. Also, no large current inrush to the lamps occurs at thetime of a pattern change so the life of the lamps is extended. And, byusing SCRs, power is delivered to the bulb only on every other halfcycle and the effect of this is to further extend the life of the lamps.

The frequency of changing lamp activation patterns may be varied simplyby appropriate adjustment of the variable resistors R2 and R3. Byadjusting these resistors, the clock pulse frequency can be varied and,of course, this varies the frequency at which a lamp pattern change ismade. i

It is to be understood that the above-described arrangement is onlyillustrative of the application of' the principles of the presentinvention. Numerous other modifications and alternative arrangements maybe devised by those skilled in the art without departing from the spiritand scope of the present invention and the appended claims are intendedto cover such modifications and arrangements.

What is claimed is:

1. A circuit for controlling the activation of a plurality of electricalelements by an A.C. supply comprising clock means for generating asequence of clock pulses,

register means for storing signal representation and for altering thestored representations in response to said clock pulses,

a clamping circuit coupled between the clock means and register meansand responsive to the A.C. supply output for preventing application ofclock pulses to the register means during every other half cycle of theA.C. supply output, and

means responsive to the signal representations stored in the registermeans for enabling the A.C. supply to activate selected ones of theelectrical elements during said every other half cycle of the A.C.supply output, the electrical elements activated being determined by thesignal representations stored in the register means.

2. A circuit as in claim 1 wherein said clock means includes adjustablemeans for varying the pulse rate of the clock pulses generated by theclock means.

3. A circuit as in claim 1 wherein said clamping circuit includes atransistor whose collector and emitter electrodes are coupled betweenground potential and the junction of the clock means and register means,and

means coupling the A.C. supply to the base electrode of said transistor.

4. A circuit as in claim 3 wherein said clamping circuit furthercomprises a diode connecting the base electrode of said transistor toground potential and wherein said coupling means includes a capacitorand resistor connected in parallel.

5. A circuit as in claim 1 wherein said enabling means includes aplurality of unilateral triode switches each having two power electrodescoupled in series with a different one of the electrical elements andthe A.C. supply, and each having a gate electrode coupled to saidregister means, said triode switches being adapted to conduct currentonly during said every other half cycle in response to certain signalrepresentations stored in said register means to thereby enableactivation of the selected electrical elements.

6. A circuit as in claim wherein said triode switches comprisesilicon-controlled rectifiers. 1

7. A circuit as in claim 1 wherein said register means is adapted toalter the stored representations in response to a second set of signalsand wherein said enabling means comprises switch means responsive to thesignal representation stored in said register means for producing saidsecond set of signals and for producing a third set of signals, andmeans responsive to said third set of signals for conducting currentfrom the A.C. supply to selected ones of the. electrical elements duringsaid every other half cycle of the A.C. supply output.

8. A circuit as in claim 7 wherein said current conmeans coupled to thelamps for enabling activation of selected ones thereof in response tosuccessively received sets of signals, said enabling means beingoperable to enable activation oflamps only during every other half cycleof the A.C. supply output,

storage means,

means for causing the storage means to successively change its contents,said causing means being operable only during half cycles of the A.C.supply output opposite said every other half cycles, and

means coupled to said storage means for producing said sets of signals,the sets of signals produced means.

10. A circuit as in claim 9 wherein said enabling 1 means comprises aplurality of unilateral triode switches, each coupled to a different oneof said lamps and each responsive to a differentsignal in each .set ofsignals.

1 l. A circuit as comprises a shift register.

12. A circuit as in claim 9 wherein said causing means comprises a clockmeans for producing a sequence of clock pulses, and a clamping circuitcoupled between the clock means and the storage means and responsive tothe A.C. supply for applying the clock pulses to the storage means onlyduring half cycles of the A.C. supply outputropposite said every otherhalf cycles, said storage means being adapted to change its contentsinresponse to received clock pulses. 13. A circuit as in claim 12wherein said clock means includes adjustable means for varying the pulserate of the clock pulses produced by the clock means.

14. A circuit as in claim9 wherein said producing means comprises atranslator for generating said sets of signals and for generatingadditional sets of signals which are a function of the contents of saidstorage means, and wherein said storage means is adapted to alter itscontents in response to said additional sets of signals,

15. A circuit for controlling the activation of a plurality ofelectrical elements by an A.C. supply comprising means responsive tosuccessively received signal patterns for selectively enabling theactivation of electrical elements by the A.C. supply in which theelectrical elements activated are determined by the received signalpatterns, and means for producing the signal patterns and for changingfrom one signal pattern output to a succeeding signal pattern output ata time corresponding to zero crossover of the A.C. supply output.

in claim 9 wherein said storage means

1. A circuit for controlling the activation of a plurality of electricalelements by an A.C. supply comprising clock means for generating asequence of clock pulses, register means for storing signalrepresentation and for altering the stored representations in responseto said clock pulses, a clamping circuit coupled between the clock meansand register means and responsive to the A.C. supply output forpreventing application of clock pulses to the register means duringevery other half cycle of the A.C. supply output, and means responsiveto the signal representations stored in the register means for enablingthe A.C. supply to activate selected ones of the electrical elementsduring said every other half cycle of the A.C. supply output, theelectrical elements activated being determined by the signalrepresentations stored in the register means.
 2. A circuit as in claim 1wherein said clock means includes adjustable means for varying the pulserate of the clock pulses generated by the clock means.
 3. A circuit asin claim 1 wherein said clamping circuit includes a transistor whosecollector and emitter electrodes are coupled between ground potentialand the junction of the clock means and register means, and meanscoupling the A.C. supply to the base electrode of said transistor.
 4. Acircuit as in claim 3 wherein said clamping circuit further comprises adiode connecting the base electrode of said transistor to groundpotential and wherein said coupling means includes a capacitor andresistor connected in parallel.
 5. A circuit as in claim 1 wherein saidenabling means includes a plurality of unilateral triode switches eachhaving two power electrodes coupled in series with a different one ofthe electrical elements and the A.C. supply, and each having a gateelectrode coupled to said register means, said triode switches beingadapted to conduct current only during said every other half cycle inresponse to certain signal representations stored in said register meansto thereby enable activation of the selected electrical elements.
 6. Acircuit as in claim 5 wherein said triode switches comprisesilicon-controlled rectifiers.
 7. A circuit as in claim 1 wherein saidregister means is adapted to alter the stored representations inresponse to a second set of signals and wherein said enabling meanscomprises switch means responsive to the signal representation stored insaid register means for producing said second set of signals and forproducing a third set of signals, and means responsive to said third setof signals for conducting current from the A.C. supply to selected onesof the electrical elements during said every other half cycle of theA.C. supply output.
 8. A circuit as in claim 7 wherein said currentconducting means comprises a plurality of triode switches, each having apair of power electrodes coupled in series with the A.C. supply and adifferent one of said electrical elements, and each having a gateelectrode, and means for applying said third set of signals to the gateelectrodes of various ones of said triode switches to cause said variousswitches to conduct current between their respective power electrodes.9. A circuit for controlling the sequence and pattern of activation of aplurality of lamps by an A.C. supply comprising means coupled to thelamps for enabling activation of selected ones thereof in response tosuccessively received sets of signals, said enabling means beingoperable to enable activation of lamps only during every other halfcycle of the A.C. supply output, storage means, means for causing thestorage means to successively change its contents, said causing meansbeing operable only during half cycles of the A.C. supply outputopposite said every other half cycles, and means coupled to said storagemeans for producing said sets of signals, the sets of signals producedbeing determined by the contents of the storage means.
 10. A circuit asin claim 9 wherein said enabling means comprises a plurality ofunilateral triode switches, each coupled to a different one of saidlamps and each responsive to a different signal in each set of signals.11. A circuit as in claim 9 wherein said storage means comprises a shiftregister.
 12. A circuit as in claim 9 wherein said causing meanscomprises a clock means for producing a sequence of clock pulses, and aclamping circuit coupled between the clock means and the storage meansand responsive to the A.C. supply for applying the clock pulses to thestorage means only during half cycles of the A.C. supply output oppositesaid every other half cycles, said storage means being adapted to changeits contents in response to received clock pulses.
 13. A circuit as inclaim 12 wherein said clock means includes adjustable means for varyingthe pulse rate of the clock pulses produced by the clock means.
 14. Acircuit as in claim 9 wherein said producing means comprises atranslator for generating said sets of signals and for generatingadditional sets of signals which are a function of the contents of saidstorage means, and wherein said storage means is adapted to alter itscontents in response to said additional sets of signals.
 15. A circuitfor controlling the activation of a plurality of electrical elements byan A.C. supply comprising means responsive to successively receivedsignal patterns for selectively enabling the activation of electricalelements by the A.C. supply in which the electrical elements activatedare determined by the received signal patterns, and means for producingthe signal patterns and for changing from one signal pattern output to asucceeding signal pattern output at a time corresponding to zerocrossover of the A.C. supply output.